In oxidative phosphorylation, what is the primary role of ATP synthase (Complex V) in the inner mitochondrial membrane?

• A. To use the proton-motive force to catalyze $ADP+P_i\to ATP$
• B. To transport $ADP$ and $ATP$ across the inner mitochondrial membrane via antiport
• C. To transfer electrons from $NADH$ to $O_2$ while pumping protons across the membrane
• D. To catalyze phosphorylation of glucose to glucose-6-phosphate in the mitochondrial matrix

Answer: (A)

Verified step by step guidance

1. Understand that ATP synthase (Complex V) is an enzyme embedded in the inner mitochondrial membrane responsible for synthesizing ATP during oxidative phosphorylation.
2. Recognize that the electron transport chain creates a proton gradient (proton-motive force) by pumping protons from the mitochondrial matrix to the intermembrane space, establishing both a chemical and electrical gradient.
3. Know that ATP synthase uses the energy stored in this proton gradient to drive the phosphorylation of ADP and inorganic phosphate (P_i) to form ATP, a process called chemiosmosis.
4. Express the reaction catalyzed by ATP synthase as: \(\text{ADP} + \text{P}_{i} \rightarrow \text{ATP}\), where the energy for this reaction comes from protons flowing back into the matrix through ATP synthase.
5. Distinguish this role from other mitochondrial processes such as electron transfer (Complexes I-IV) or transport of nucleotides, confirming that ATP synthase's primary function is to harness the proton-motive force to produce ATP.